Preheat oven to 375 degrees F (190 degrees C).
In a mixing bowl, beat eggs on high for 5 minutes. Gradually beat in white sugar until thick and lemon-colored. Add pumpkin and lemon juice.
In another bowl combine flour, cinnamon, baking powder, salt, and nutmeg; fold into the pumpkin mixture.
Grease a 15x10x1 inch baking pan; line with waxed paper. Grease and flour the paper. Spread batter into pan; sprinkle with walnuts.
Bake at 375 degrees F (190 degrees C) for 15 minutes or until cake springs back when lightly touched.
Immediately turn out onto a linen towel dusted with confectioners' sugar. Peel off paper and roll cake up in the towel, starting with the short end. Cool.
Meanwhile, in a mixing bowl, beat cream cheese, 1 cup confectioners' sugar, butter, and vanilla until fluffy.
Carefully unroll the cake. Spread filling over cake to within 1 inch of edges. Roll up again. Cover and chill until serving. Dust with additional confectioners' sugar, if desired.